In the Name of Allah we enter , in the Name of Allah we leave , and upon our Lord we depend [then say As-Salaamu 'Alaykum to those present].

Reference: Abu Dawud 4/325. Muslim {Hadith no. 2018) says that one should mention the Name of Allah when entering the home and when beginning to eat; and that the devil, hearing this, says: "There is no shelter for us here tonight and no food."